docs: def normalize(numbers, total=1.0):  #from AI: A Modern Appproach
      """Multiply each number by a constant such that the sum is 1.0 (or total).
      >>> normalize([1,2,1])
      [0.25, 0.5, 0.25]
      """
      k = total / sum(numbers)
      return [k * n for n in numbers]